1. Field of the Invention
The present invention relates to a workpiece positioning apparatus for a machine tool using an imaging unit such, for example, as vision sensor.
2. Description of the Related Art
In some cases, a workpiece is formed with two feature points for example, such as holes, bosses, notches or the like for positioning or phase-matching. Such feature points are engaged with a pin, spigot joint, or butt provided on the table of the machine tool to achieve positioning and phase-matching of the workpiece. In Japanese Examined Patent Publication No. 07-004737, a reference hole is formed in a workpiece as a feature point. An imaging unit, e.g., a camera images the reference hole of the workpiece through a hole formed through a table.
In order to achieve more accurate positioning or the like, a touch probe is used which is mounted on a spindle of a machine tool. Preferably, the workpiece is positioned and phase-matched using together an electric contact sensing technique by the touch probe and the above-described technique using the feature point. Further, in Japanese Patent No. 4,840,144 Specification, a device is disclosed which is configured to non-contact measure a distance between a workpiece and a sensor.